As mobile devices have been increasingly developed, and the demand for such mobile devices has increased, the demand for secondary batteries has also sharply increased. Among such secondary batteries is a lithium secondary battery exhibiting high energy density and operating voltage and excellent charge retention and service-life characteristics, which has been widely used as an energy source for various electronic products as well as mobile devices.
However, various kinds of combustible materials are contained in the lithium secondary battery. As a result, the lithium secondary battery may be heated or explode due to the overcharge of the battery, the overcurrent in the battery, or external physical impact. That is, the safety of the lithium secondary battery is very low. Consequently, safety elements, such as a positive temperature coefficient (PTC) element and a protection circuit module (PCM), to effectively control an abnormal state of the lithium secondary battery, such as the overcharge of the lithium secondary battery or the overcurrent in the lithium secondary battery, are mounted to a battery cell in a state in which the safety elements are connected to the battery cell.
Generally, the PCM is connected to the battery cell via conductive nickel plates by welding. That is, the nickel plates are connected to electrode tabs of the PCM by welding, and then the nickel plates are connected to electrode terminals of the battery cell by welding. In this way, the PCM is connected to the battery cell to manufacture a battery pack.
It is required for the safety elements, including the PCM, to be maintained in electrical connection with the electrode terminals of the battery cell and, at the same time, to be electrically isolated from other parts of the battery cell.
Meanwhile, an operation of coupling components, including a protection circuit member such as a PCM, to the upper end of a battery cell is performed on a battery pack assembly line. The construction of such an assembly line may be changed as needed. Generally, the assembly line is configured such that a metal clad, an insulative mounting member, a protection circuit module, and an insulative top cap may be sequentially coupled to the upper end of the battery cell.
In a case in which different kinds of battery cells are assembled, however, different assembly lines must be configured based on the kinds and sizes of the battery cells with the result that manufacturing cost is increased. Furthermore, assembly time is increased, and therefore, assembly efficiency is lowered.
In order to solve the above problems, therefore, there is a high necessity for a technology that is capable of assembling battery cells having different sizes on a single assembly line, thereby improving manufacturing efficiency and productivity of a battery pack.